Adjustable frequency horn



Nov. 11, 1969 w. s. JENSEN 3,477,405

ADJUSTABLE FREQUENCY HORN Filed July 19, 196'.

2 Sheets-Sheet l W/LL/AM G. JENSEN INVENTOR ATTORNEYS Nov. 11, 1969 w. G. JENSEN 3,477,405

ADJUSTABLE FREQUENCY HORN Filed July 19, 1967 2 Sheets-Sheet 2 WILL/AM G. JENSEN INVENTOR ATTORN EYS United States Patent O US. Cl. 116-137 Claims ABSTRACT OF THE DISCLOSURE A horn or sound projector suitable for use in an automotive vehicle in which the frequency of the sound emitted from the horn may be adjusted over wide limits. The horn has two spirally shaped air passages, separated by a sound barrier or guide therebetween having an aperture, and a deflection means within the passages. The position of the aperture and this deflection means may be suit-' ably adjusted to adjust the lengths of the air passages.

thereby varying or adjusting the frequency of the sound.

emitted therefrom.

BACKGROUND OF THE INVENTION 1 This invention pertains to a horn or sound projecting means suitable for use on an automotive vehicle in which the frequency of the sound emitted may be adjusted over wide limits.

In the prior art horns known to the applicant, the frequency of the sound emitted by the horn is a function of the dimensions of the various structural components of the horn and is determined by the relative sizes of these components. For example, to produce sounds of low frequency from a horn, it is necessary to provide a large structure; particularly, with respect to the diameter of the vibratory horn diaphragm and to the length of the air passages that receive the air waves generated by the vibratory horn diaphragm. If higher frequency sounds are desired, it is necessary in prior art devices to reduce the dimensions of the structural components of the horn including the vibratory horn diaphragm that generates the sound waves emitted by the horn and the length of the air passages that receive the sound Waves generated by the horn.

The present invention provides a variable frequency horn or sound projector in which the dimensions of the structural components may remain constant. Means are provided in the born for varying the length of the air passages in the horn to correlate this length with the resonant frequency of a vibratory horn diaphragm or sound generating means. Therefore, it is possible with the present invention to provide a single sized horn structure which is capable of being adjusted to provide varying frequencies of the sound emitted by the horn or sound projector.

SUMMARY OF THE INVENTION The present invention provides a horn or sound projector capable of use on an automotive vehicle in which the sound emitted may be varied over wide frequencies without changing the dimensions of the structural components of the horn or sound projector. This is accomplished by the use of two generally spirally shaped air passages which are complementary in shape and have their axes positioned generally parallel to one another. A separating plate positioned in a plane generally parallel to these two axes separates the two air passages. Means are provided to permit communication through the plate between the two air passages with deflection means positioned in the two air passages for deflecting sound from one of the air passages to the other. The plate may be 3,47 7,405 Patented Nov. 11, 1969 rotation so that the deflection means and. the aperture are positioned at various locations along the length of the two air passages to thereby vary the length of each of the passages. As a result, the frequency of the sound emitted by the horn may be adjusted over wide limits.

In the preferred form of the invention, the means for generating the air waves which will produce the sound comprises a vibratory horn diaphragm of a standard type which is coupled to one of the spirally shaped air passages. The sound Waves travel thr'ou'gbthis first air passage and strike the deflecting means positioned in it. This causes the sound waves to be deflected through the aperture in the separating plate and into the second spirally formed air passage where the sound is again deflected by the deflection means so that it travels through this second spirally shaped air passage. The sound is thereafter emitted to the atmosphere through a suitable trumpet or other equivalent sound projecting means.

As stated above, the aperture in the adjustable plate means and the deflecting means may beadjustably positioned to adjust the length of the first spirally shaped air passage and the second spirally shaped air passage. These lengths should be adjusted so that the length of each of them is approximately equal to one-eighth of the wave length of the sound wave generated by the sound generating means. As previously mentioned, this sound generating means may be a vibratory horn diaphragm which is vibrated by a vibratory motor at the natural frequency of the horn diaphragm. Thus, horn diaphragms of varying natural frequencies may be employed and the position of the sound deflecting means and the aperture in the plate described above may be adjustably positioned to adjust the length of each of the spirally shaped air passages so that the length of each of them equals one-eighth of the wave length of the sound wave generated by the vibration of the horn diaphragm at its natural frequency.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a longitudinal, sectional view partially in elevation of the born or sound projector of the present invention.

FIGURE 2 is an end view, with a portion of the separating plate cut away, of one section of the horn or sound projector means of the present invention.

FIGURE 3 is'a projected view projected from FIG- URE 1 and showing the sound deflecting means of the present invention. 7

FIGURE 4 is a plan View of the" sound separator or guide of the present invention; and i i FIGURE 5 is an end elevational view with a portion of the separating plate cut away of the second section of the horn or sound projecting means of the present invention.

DETAILED DESCRIPTION OF THE INVENTION- Referring now to the drawings in which like reference numerals designate like parts throughout the several views thereof, there is shown in FIGURE I a longitudinal, sectional view of the present invention partially in elevation and showing a conventional vibratory horn motor 10 that is adapted to be attached to an automotive vehicle by means of a bracket 12. The vibratory horn motor 10 actuates a diaphragm 14 of the vibratory type in a conventional manner. It can be appreciated that the horn motor 10 and the coupling of it to the diaphragm 14 are of standard construction and that as the horn motor 10 actuates the horn diaphragm 14, it will vibrate at its natural frequency thereby producing sound waves having a frequency which is equal to thenaturalfrequency. of vibra= tion of the horn diaphragm 14.

The sound projector or horn of the present invention includes a first section 16 having a generally spirally shaped air passage 18 formed by spaced walls 20 and 22 preferably of cylindrical configuration and by an intermediate connecting wall 24. As can best be seen by reference to FIGURE 1, the sound waves generated by the vibration of the horn diaphragm 14 are projected into this generally spirally shaped air passage 18 by means of a chamber 26 that has a deflecting plate or wall 28 formed at an acute angle, preferably 45, with respect to the plane ofthe diaphragm 14 and to the axis of the generally spirally shaped sound passage 18.

The first section 16 of the horn or sound projector has an annular flange 29 that is coupled to an annular flange 30 of the horn motor 10 by a plurality of rivets or suitable fastening devices 32 spaced circumferentially about the annular flange 29 on the first section 16 and the annularly extending flange 30 on the horn motor 10. These rivets 32 not only connect the first section 16 of the horn or sound projector and the horn motor 18, but also serve as a means for positioning and holding the horn diaphragm 14 in a proper position with respect to the horn motor 10 and the first section 16 of the horn or sound projector.

Thus, as sound waves are generated by the vibration of the horn diaphragm 14 at its natural frequency, the sound waves are projected into the chamber 26 positioned in the first section 16 and they reflect off the angularly inclined wall 28 which, as stated above, is preferably positioned at a angle with respect to the horn diaphragm 14 and into the generally spirally shaped air passage 18 positioned in the first section 16 of the horn or sound projector of the present invention.

A second section 38 of the horn diaphragm has a generally spirally shaped air passage 42 that is complei mentary in form to the generally spirally shaped air passage 18 formed in the first section 1.6. This generally spirally shaped air passage 42 is formed by means of generally cylindrical walls 44 and 46 that are joined by another or third wall 48. Similarly, this second section has a chamber 49 including an angularly inclined deflecting wall 50 positioned at an acute angle, preferably 45, with respect to the axis of the generally spirally shaped air passage 42. As the sound waves travel through the generally spirally shaped air passage 42, they are deflected against the wall 50 and are directed into a trumpet 52 so that the sound waves may be projected therefrom. This trumpet may have a screen 54 positioned over its opening to permit the passage of the air molecules outwardly through the trumpet 52. This screen 54 not only permits the passage of the air molecules through it but it also blocks the passage of water molecules and dirt that may enter the horn from the atmosphere.

The generally spirally shaped air passage 18 formed in the first section 16 and the generally spirally shaped air passage 42 formed in the second section 38 of the horn are separated by means of a generally annular shaped fiat plate 60. This generally annular shaped flat plate has a pair of radially outwardly extending tabs 62 and 64, as well as, a radially outwardly extending tab 66 that is of relatively greater circumferential extent than the two tabs 62 and 64. An aperture 70 in plate 60 is positioned radially inwardly from the radially extending tab 66 and is of generally rectangular configuration. This aperture, as can best be seen with reference to the dotted lines shown in FIGURE 2, extends in radial dimension across the generally spirally shaped air passage 18, as well as, across the generally spirally shaped air passage 42 positioned in the second section 38 of the horn. It, therefore, connects or couples the air passage 18 positioned in the first section 16 of the horn or sound projector of the present invention and the air passage 42 formed in the second section 38 of the horn or sound projector of the present invention.

The generally annular flat plate 60 is positioned properly between the two sections 16 and 38 of the horn or sound projector of the present invention by means of locating washers 72 positioned around the fastening means which may be in the form of integrally formed rivets or screws 74 that connect the first section 16 and the second section 38 of the horn or sound projector of the present invention.

A deflector having a first leg 82 and a second leg 84 is positioned to deflect the sound waves present in the generally spirally shaped air passage 18 into the generally spirally shaped air passage 42 formed in the second section 38. To accomplish this, the first leg 82 of the sound deflecting means 80 is positioned at an acute angle, preferably 45, with respect to the axis of the first generally spirally shaped air passage 18 formed in the first section 16 of the horn or sound projector of the present invention and the second leg 84 is positioned at an acute angle, preferably 45, with respect to the axis of the generally spirally shaped passage 42 formed in the second section 38 of the horn or sound projector of the present invention. As shown in the drawings, particularly with reference to FIGURES '2, 3 and 4, the sound deflecting means 80 comprising the two legs 82 and 84 may be aflixed to the generally annular flat separating plate 60 that separates the spirally formed air passages 18 and 42 positioned in the first section 16 and the second section 38, respectively, by means of a pair of radially spaced rivets 86 and 88 that pass through and affix parallel extending tabs 90 and 92 positioned on the legs 82 and 84, respectively, to the generally annular shaped fiat plate 60.

The legs 82 and 84 of the deflecting means 80 may have generally parallel extending extremities 96 and 98, respectively, which are positioned in engagement with parallel extending walls 100 and 102 formed on the first horn section 16 and the second horn section 38, respectively, to provide an extended sealing means for the air that is forced through the generally spirally shaped air passages 18 and 42, respectively, positioned in the two sections.

It can be readily appreciated that the generally annular flat plate 60 may be rotated within given limits with respect to the first section 16 and the second section 38 of the horn or sound projector means of the present in vention so that the deflecting legs 82 and 84 together with the aperture 70 positioned in the flat separating plate 60 may be located at various positions with respect to the generally spirally shaped air passages 18 and 42 positioned in the first section 16 and the second section 38, respectively. This will shorten or lengthen the effective length of the air passage 18 and 42, respectively; and as a result, the frequency of the sound emitted by the horn or sound projector of the present invention may be altered or varied in accordance with this position. It can readily be appreciated that the horn diaphragm 14 should be selected to have a natural frequency of vibration which will emit sound waves having a wave length equal to oneeighth of the length of the generally spirally shaped air passages 18 and 42, respectively, positioned within the first section 16 and the second section 38 of the horn or sound projector of the present invention.

It can be readily appreciated that the deflecting means 80 need not be coupled directly to the flat annular plate 60, but that it may be a separate V-shaped component that will pass through the aperture 80. In this case, guide means in the form of flat shelves or protrusions may be positioned along the length of the generally spirally formed an passages 18 and 42 to receive this generally V-shaped deflection means at various locations along the length of the generally spirally shaped air passages 18 and 42.

As a result of the structure described above, a variable frequency horn or sound projector is provided that will permit the varying of the frequency of sound emitted without a change in the dimensions of the horn structure. All that needs to be done is to position the aperture in the annular separating plate and the sound deflecting means at a position where the desired frequency will be obtained and to provide a horn diaphragm having a matching natural frequency of vibration which will emit a sound wave having a wave length equal to four times the combined length of the generally spirally shaped air passages positioned in the first horn section and the second horn section.

The adjustable frequency horn of this invention will have many apparent modifications to those skilled in the art.

What is claimed is:

1. In a horn, means for generating sound waves, a first section having a generally spirally shaped Wall means forming a first generally spirally shaped air passage coupled to said means for generating sound waves, a second section having a generally spirally shaped wall means forming a second generally spirally shaped air passage complementary to and positioned adjacent said first generally spirally shaped air passage, means coupled to said first and said second sections for separating said first and said second generally spirally shaped air passages, and adjustable means coupled to said first and said second sections and said generally spirally shaped air passages for adjusting the length of said first and said second generally spirally shaped air passages and for deflecting sound Waves from said first generally spirally shaped air passages into said second generally spirally shaped air passage whereby the frequency of the sound emitted from said horn may be adjusted.

2. The combination of claim 1 in which the axes of said first and said second generally spirally shaped air passages are positioned generally parallel to one another.

3. The combination of claim 2 in which said means for separating said first and said second generally spirally shaped air passages comprises a generally fiat plate positioned substantially parallel to the axes of said first and said second generally spirally shaped air passages.

4. The combination of claim 3 in which said generally flat plate has an aperture positioned therein and said means for deflecting sound waves from said first generally spirally shaped air passage into said second generally spirally shaped air passage is positioned adjacent said aperture and deflects sound waves from said first generally spirally shaped air passage into said second generally spirally shaped air passage through said aperture.

5. The combination of claim 4 in which said plate may be rotated with respect to said sections and said generally spirally shaped air passages to position said aperture at various positions in said air passages and means are provided for positioning said means for deflecting sound waves at various positions adjacent said aperture when said plate is rotated to position said aperture at said various positions with respect to said first and said second generally spirally shaped air passages.

6. The combination of claim 5 in which said means for deflecting sound between said first generally spirally shaped air passage and said second generally spirally shaped air passage compries a generally V-shaped element having a first leg positioned in said first generally spirally shaped air passage and a second leg positioned in said second generally spirally shaped air passage.

7. The combination of claim 6 in which the angle defined between said first leg and said second leg of said generally V-shaped element is approximately 90 and the juncture of said first and said second legs is positioned substantially in the plane of said generally flat plate that separates said first and said second generally spirally shaped air passages.

8. In a horn adapted for use on an automotive vehicle the combination comprising a vibratory horn diaphragm, motor means coupled to said horn diaphragm for vibrating said horn diaphragm, a first section having spirally shaped wall means forming a first generally spirally shaped air passage having an axis positioned generally parallel to said horn diaphragm, a second complementary formed section having spirally shaped wall means forming a generally spirally shaped air passage having an axis positioned generally parallel to said horn diaphragm, a fiat plate positioned between said first section and said second section and between said first generally spirally shaped air passage and said second generally spirally shaped air passage, said flat plate having an aperture positioned therein, deflection means positioned adjacent said aperture for deflecting sound Waves from said first generally spirally shaped air passage into said second generally spirally shaped air passage through said aperture, said deflection means comprising a generally V- shaped element positioned adjacent said aperture in said plate and having a first leg positioned in said first generally spirally shaped air passage and :a second leg positioned in said second generally spirally shaped air passage with the junction of said first and said second legs positioned in the plane of said flat plate, said generally flat plate including means for rotating said generally flat plate to adjust the position of said aperture with respect to said first and said second generally spirally shaped air passages, and means for adjusting the position of said V-shaped element commensurate with the position of said aperture whereby the frequency of the sound waves emitted by said horn may be varied by varying the length of said first and said second generally spirally shaped air passages.

9. The combination of claim 8 in which the angle between said first leg and said second leg of said generally V-shaped element is approximately 10. The combination of claim 9 in which the length of the first generally spirally shaped air passage and the length of said second generally spirally shaped air passage each are adjusted by the movement of said plate and said V-shaped element to approximately one-eighth of the wave length of the sound waves produced by the vibration of said vibratory horn diaphragm at its resonant frequency.

References Cited UNITED STATES PATENTS 284,492 -9/ 1883 Schweich 84-387 1,015,622 1/1912 Hunter. 1,810,708 6 1931 Hutchison. 1,832,763 11/1931 Campbell 181-473 1,841,535 1/1932 Hueber et a1. 116-142 1,883,458 10/1932 Aufiero 116-442 1,941,324 12/1933 Schirmer 116-140 2,642,895 6/1953 Bertin et a1. 3,124,098 3/1964 Thoben 116-142 LOUIS R. PRINCE, Primary Examiner DANIEL M. YASICH, Assistant Examiner U.S. Cl. X.R. 340-388 

